1. Field of the Invention
The present invention relates to a motor actuator used, for example, in a power window device that moves a window glass of a vehicle door up and down or in a sunroof device that moves a sunroof panel forward and backward.
2. Description of Related Art
Generally, a power window device and a sunroof device have a motor as a drive source. For instance, JP-A-8-29114 and JP-A-9-236431 respectively disclose a motor actuator having a feature capable of detecting a rotational position of an output shaft of such a motor, i.e., a position of a window glass or a sunroof panel.
The above-disclosed motor actuator has a motor and a position detector that are connected with each other. The position detector includes a planetary gear train unit, a switch portion and a clutch mechanism. The planetary gear train unit has a ring gear rotatably supported within a cover plate, planetary gears meshed with the ring gear and a sun gear. The switch portion includes moving contacts and fixed contacts. The moving contacts are integrally formed in the ring gear of the planetary gear train unit to rotate therewith. The fixed contacts are fixed to the cover plate and are allowed to engage with the corresponding moving contacts. The clutch mechanism disables transmission of a rotational force from the moving body (output shaft of the motor) to the ring gear in a forward direction. Furthermore, the position detector includes a sensor drive shaft for driving the ring gear. The sensor drive shaft has the sun gear integrated therein and is connected to the motor output shaft of the motor. Thus, when the motor output shaft is rotated, the ring gear is rotated integrally with the moving contacts. The rotation of the moving contacts causes activation of the switch portion. The activation of the switch portion allows detection of a rotational position of the motor output shaft, i.e., a position of the window glass or the sunroof panel.
In the above-described motor actuator, the motor output shaft and the sensor drive shaft are connected with each other by a complex interfitting structure (geometrically complex) to synchronously (integrally) rotate the sun gear with the moving body, such as the motor output shaft. That is, the motor output shaft has a hollow structure including axial splines around its outer peripheral surface to form a spline interfitting portion. The sensor drive shaft has a corresponding spline interfitting portion that meshes with the spline interfitting portion of the motor output shaft. To guide the engagement between the two spline interfitting portions, a plurality of axially extending guide grooves are formed in an inner peripheral surface of the motor output shaft. Furthermore, a cylindrical portion that can be interfitted within the motor output shaft is provided at a distal end of the sensor drive shaft, and a plurality of guide projections that correspond: with the guide grooves are formed around an outer peripheral surface of the cylindrical portion. To couple the motor output shaft with the sensor drive shaft, the guide projections of the sensor drive shaft are inserted into the corresponding guide grooves of the motor output shaft, and the spline interfitting portion of the sensor drive shaft are meshed with the spline interfitting portion of the motor output shaft.
However, in the above-described interfitting structure used for the above motor actuator, a complicated and costly manufacturing process is required for manufacturing each interfitting portion with: a high degree of accuracy. Furthermore, interfitting positions of the guide grooves and the corresponding guide projections are closely related to interfitting positions of the spline interfitting portion of the motor output shaft and the spline interfitting portion of the sensor drive shaft. As a result, it is difficult to maintain a high degree of accuracy with respect to these interfitting positions and to prevent production of a defective motor output shaft or sensor drive shaft that cannot be properly interfitted With the corresponding sensor drive shaft or motor output shaft, resulting in higher costs.
In view of the foregoing problems, it is an object of the present invention to provide a motor actuator that is capable of detecting a position of a moving object, such as a window glass, a sunroof panel or the like, with a high degree of accuracy at low costs by use of a simple structure and that does not require a high quality control of an interfitting connection (engagement connection) between a motor output shaft and a sensor drive shaft to permit easy manufacturing and assembly of the motor output shaft and the sensor drive shaft.
To achieve the objective of the present invention, in a motor actuator including a motor and a position detector, an approximately cylindrical motor output shaft of the motor has a radial recess that recesses radially outward from an inner peripheral surface, a shaft portion of a sensor drive shaft of the position detector has a radial projection that protrudes from an outer peripheral surface of the shaft portion to be engaged with the radial recess. of the motor output shaft, and the motor output shaft and the sensor drive shaft are non-rotatably connected with each other by engagement of the radial recess of the motor output shaft with the radial projection of the sensor drive shaft. Accordingly, a connection between the motor and the position detector can be readily accurately performed by a simple structure. Thus, the motor output shaft and the sensor drive shaft can be readily manufactured and assembled in a low cost. As a result, when the motor actuator is applied to a moving object such as a window glass, a sunroof panel or the like, a position of the moving object can be readily accurately detected in low cost.
Preferably, an axial end portion of the radial projection is provided to be tapered toward its axial end. Therefore, when the motor output shaft and the sensor drive shaft are connected, the radial projection can be readily accurately fitted into the radial recess of the motor output shaft.